1. Field of the Invention
This invention relates to an evaluation method for semiconductor devices, and more particularly to an evaluation method for semiconductor devices for measuring the distribution of potential o the surface and in the internal portion of the semiconductor device.
2. Description of the Related Art
Conventionally, a method is developed to analyze the abnormality in two-dimensional diffusion of depletion layer and crystal defect in a semiconductor device. In this method, the PN junction of the semiconductor device is reversely biased, and a light beam focused by a lens or the like is scanned on the surface of the semiconductor device. At this time, photo-induced current flows across the PN junction of the semiconductor device. The current is detected in position corresponding to the scanning position, and an image is displayed with brightness corresponding to the detected current value on a monitoring screen. The image is known as an optical beam induced current (OBIC) image, and the two-dimensional diffusion of depletion layer and crystal defect in the semiconductor device can be analyzed based on variation in brightness in the OBIC image.
Thus, the evaluation of the semiconductor device is conventionally effected based on the qualitative analysis.
For example, potential inside the semiconductor device can be attained by causing the CAD system to effect simulation in the designing stage of the semiconductor device. However, in the prior art, the potential is not actually measured.